Glycerol-derived ester oligomers from cork suberin

The cork suberin polyester was partially depolymerized by a methanolysis reaction catalyzed by calcium hydroxide. The methanolisate was analysed by ESI-MS/MS in the form of [M + Li]+ adduct-ions. This reaction solubilized a mixture of monomers and oligomers, including a set of glycerol-derived dimeric and trimeric esters. Four types of glycerol esters were identified: monoacylglycerols of α,ω-diacids, of ω-hydroxyacids and of monoacids; diglycerol diesters of α,ω-diacids; diacylglycerols of α,ω-diacids; monoacylglycerols of linear dimeric esters of α,ω-diacids and ω-hydroxyacids. The α,ω-diacids and ω-hydroxyacids found as monomer residues in the glycerol esters are the main ones found as cork suberin monomers. It is concluded that suberin is a glycerol-derived lipid of polymeric dimensions. Due to the protective and insulating role that it plays in plants, suberin should be considered together with the other known glycerolipids that build up biological membranes.